1. Field of the Invention
This invention relates generally to detection of intrusion into electronic assemblies, and more particularly, to the detection of intrusion by mechanical or chemical means for the purpose of reading the data stored in a memory.
In many computer applications, it is desirable to protect the contents of the computer memory from being unlawfully or unauthorizedly extracted and read. It is conventional practice to prevent reading of information electronically by providing certain encryption schemes wherein data is transmitted and received in an encrypted form and only authorized people who have the decryption key are able to read the data. There are many different types of encryption schemes which are useful in protecting the sensitive data against being read by unauthorized persons. Encryption keys and other sensitive data are often stored in I/C (integrated circuit) memory components within the computer. By use of software, the stored information is generally adequately protected from unauthorized persons using keyboard entries to attempt memory interrogation. However, an unauthorized person with the necessary skills and knowledge, and sufficiently motivated can by-pass software controls and attack the computer hardware directly. There are many attacks some straight forward and well known, others more sophisticated, that allow direct interrogation of memory components and devices. One scheme of protection against such attacks is to provide some type of detecting means which detect any attempted mechanical intrusion into the sensitive area of the computer and, when such intrusion is detected an alarm is given and/or a signal is sent to circuitry, which circuit erases the data, thereby preventing the compromise of the information which was stored in the computer memory components. Various schemes have been proposed which provide for some type of electronic or electrical grid surrounding the computer circuitry and, when this electrical grid is broken or breached, the requisite signal is generated. Schemes for such electronic detection are shown in U.S. Pat. No. 4,446,475 and 3,594,770. These types of systems, however, have several drawbacks. One such drawback is that many grids are susceptible to very careful mechanical manipulation to allow the memory device to be accessed without breaking or otherwise compromising the circuit. Also, certain of these systems are susceptible to a type of attack wherein the materials which support the electrical grid are chemically attacked leaving access areas exposed to circumvent the electrical grid thus allowing physical intrusion into the memory components.
Still other more sophisticated attacks, through temperature modification or though ionizing radiation (e.g. x-rays) affect volatile memory devices such that an erasure command is not effective, thereby allowing the electrical wrapping to be circumvented.
The present invention overcomes these defects by providing an outer intrusion detection layer that is highly resistant to chemical and mechanical attacks. Further, internal circuitry is provided to detect temperature and ionizing radiation attacks.
Use of detection for low temperatures to prevent tampering is shown in U.S. Pat. No. 4,593,384. Also, temperature responsive devices for safeguarding information are shown in U.S. Pat. No. 3,851,602. The use of means to limit effects of ionizing radiation are shown in U.S. Pat. Nos. 4, 413,327 and 4,639,826. However, neither of these patents suggest any means of security protection and/or erasing of information responsive to very high levels of radiation applied for purpose of attacking a volatile memory device to obtain sensitive information.